For example, there is a technique described in Japanese Patent Application Publication No. 2006-311733 (JP 2006-311733 A) (Patent Document 1) as related art of such coils as described above. Patent Document 1 discloses a coil having two star connections (Y-connections), in which a common neutral point having respective one ends of phase coil portions of each phase connected thereto is provided for the two star connections. In the configuration described in Patent Document 1, each of the two phase coil portions of the same phase which form a parallel circuit (series coil A and series coil B shown in FIG. 5 of Patent Document 1) is formed by two coil groups that are arranged so as to face each other in the radial direction, as shown in FIG. 4 of the document. Thus, even if a stator around which the coil is wound and a rotor that is placed so as to be rotatable with respect to the stator are eccentric with each other, electromagnetic balance is maintained, and generation of a circulating current in the parallel circuit can be suppressed.
In the configuration of Patent Document 1, however, another coil group forming another phase coil portion of the same phase is placed between the two coil groups forming the same phase coil portion in the circumferential direction. This requires jumper lines connecting the two coil groups to be placed so as to overlap another coil group in the circumferential direction. The configuration of Patent Document 1 therefore complicates a coil winding process of winding the coil around a core, and may increase time required for the coil winding process and cost of facilities for the coil winding process.